Loch Leven, UK: long-term (1985 to 2016) phosphorus dynamics in a shallow lake and its implications for water-quality management

Loch Leven is a shallow eutrophic lake in the UK with a history of eutrophication problems. Here, we document the response of internal phosphorus cycling within the lake to a reduction in catchment phosphorus load from 5.25 mg total phosphorus (TP) m-2 d-1 (1985) to between 1.44 mg TP m-2 d-1 and 2.39 mg TP m-2 d-1 (1995, 2005, 2015). Since 1989, internal loading has resulted in elevated summer TP concentrations, although the magnitude of the summer peak load has varied between about 3.5 and 0.3 mg P m-2 d-1. This variation can be explained, at least partly, by fluctuations in spring wind speed and temperature, and summer precipitation, mediated through a series of complex ecological and biogeochemical interactions. We present an empirical model that predicts the effects of future climate change on internal loading and offer recommendations for the development of short-term forecasting approaches linked to large-scale teleconnection indices, such as the North Atlantic Oscillation.